1. Field of the Invention
The present invention generally relates to microphones and apparatuses based on the use of microphones, and particularly relates to condenser microphones and apparatuses based on the use of such microphones.
2. Description of the Related Art
Technology has been making progress in terms of reducing the size and weight of electrical equipment, and sound processing apparatuses such as portable recorders and cellular phones are not an exception. Such sound processing apparatuses typically employ condenser microphones, which are comprised of two plates, i.e., a diaphragm and a back plate.
Microphones of this kind provide superior performance in terms of sensitivity and noise robustness, and are suitable for size reduction. The diaphragm and the back plate are packed in a case with a spacer (support block) placed therebetween, thereby being provided as a single module, which is then implemented on a circuit board for use in the sound processing apparatus.
Such conventional microphones are manufactured by assembling a plurality of different components, thereby resulting in drawbacks as follows.
Because of the limitations of preciseness during an assembly process, there is an inevitable limit to size reduction. The thickness and circuit area of microphone modules tend to be relatively large, compared to other modules of semiconductor devices implemented on small-size electrical equipment such as cellular phones. This hinders an effort toward increasing the circuit density of circuit boards.
Since the used materials differ from component to component, and thus have different thermal expansion coefficients, distortion may occur due to heat applied during a heat process (more than 200 degrees Celsius) such as a soldering process, which is repeated multiple times during the circuit implementation. Where lead-free solder is used during the circuit implementation process, higher temperature such as in the range from 240° C. to 260° C. need to be taken into consideration.
Further, if components based on resin materials are employed for the diaphragm and the spacer insulator, for example, these components cannot be treated with other components during a high-temperature implementation process such as the bump/reflow process. This results in inability to pursue efficiency.
Accordingly, there is a need for a microphone that is formed as a silicon-based chip, thereby achieving size reduction, cost reduction, and sufficient reliability.